Vehicle Pre-Impact Sensing System Having Signal Modulation

ABSTRACT

A vehicle pre-impact sensing system is provided that includes an array of energy signal transmitters mounted on a vehicle for transmitting signals within multiple transmit zones spaced from the vehicle and an array of receiver elements mounted on the vehicle for receiving signals reflected from an object located in one or more multiple receive zones indicative of the object being in certain one or more zones. A processor processes the received reflected signals and determines range, location, speed and direction of the object, determines whether the object is expected to impact the vehicle as a function of the determined range, location, speed and direction of the object, and generates an output signal indicative of a pre-impact event. The system may detect one or more features of a target object, such as a front end of a vehicle. Additionally, the system may modulate the transmit beams. Further, the system may perform a terrain normalization to remove stationary items.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. §119(e) to U.S.Provisional Patent Application No. 61/130,236, filed on May 29, 2008,the entire disclosure of which is hereby incorporated herein byreference.

TECHNICAL FIELD

The present application generally relates to vehicle crash sensing and,more particularly, relates to a system and method of sensing an imminentcollision of an object with a vehicle prior to impact.

BACKGROUND OF THE INVENTION

Automotive vehicles are commonly equipped with passenger restraint andcrash mitigation devices such as seat belts, front air bags, side airbags and side curtains. These and other devices may be deployed in theevent of a collision with the host vehicle to mitigate adverse effectsto the vehicle and the occupants in the vehicle. With respect toactivated devices, such as air bags and side curtain bags, these devicesgenerally must be deployed quickly and in a timely fashion. Typically,these types of devices are deployed when sensors (e.g., accelerometers)mounted on the vehicle sense a severe impact with the vehicle.

In some vehicle driving situations, it is desirable to determine theonset of a collision, prior to impact of an object with the hostvehicle. For example, vision systems employing cameras may be used tomonitor the surrounding environment around the vehicle and the videoimages may be processed to determine if an object appears to be on acollision path with the vehicle. However, visions systems are generallyvery expensive and suffer a number of drawbacks.

An alternative approach is disclosed in U.S. Patent ApplicationPublication No. 2009/0099736, assigned to the assignee of the presentapplication. The approach set forth in the aforementioned patentapplication discloses a vehicle pre-impact sensing system that transmitsa plurality of infrared (IR) beams and receives a plurality of beamswithin a plurality of curtains incrementally spaced from the hostvehicle for sensing objects that may impact the side of the hostvehicle. The aforementioned published patent application is herebyincorporated herein by reference.

It would be desirable to provide for an enhanced cost-effective systemthat senses a collision prior to impact with the host vehicle,particularly for use to detect side impact events.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a vehicle pre-impactsensing system is provided that includes an array of energy signaltransmitters mounted on a vehicle for transmitting energy signals withinmultiple transmit zones space from the vehicle. The system furtherincludes an array of receiver elements mounted on the vehicle forreceiving the signals reflected from an object located in one or moremultiple receive zones indicative of the object being in certain one ormore receive zones. The system also includes a processor for processingthe received reflected signals and determining range, location, speedand direction of the object. The processor further modulates thetransmit energy signals and determines (e.g., measures) a difference insensed signals for each zone with the transmitter turned on and turnedoff. The processor also determines whether the object is expected toimpact the vehicle as a function of the determined range, location,speed and direction of the object, and generates an output indicative ofa sensed pre-impact event.

According to another aspect of the present invention, a method ofdetecting an expected impact of an object with a vehicle is provided.The method includes the steps of transmitting signals within multipletransmit zones incrementally spaced from the vehicle, within one zone ata time, receiving signals reflected from an object located in the one ormore multiple zones indicative of the object being in certain one ormore received zones and processing the received reflected signals. Themethod also determines a location of the object, determines a range tothe object, determines speed of the object, determines direction of theobject and modulates the transmit energy signals array. The method alsodetermines a difference in sensed signals for each zone with thetransmitter turned on and off and determines whether the object isexpected to impact the vehicle as a function of the determined range,location, speed and direction of the object, and generating an outputindicative of the sensed pre-impact event.

These and other features, advantages and objects of the presentinvention will be further understood and appreciated by those skilled inthe art by reference to the following specification, claims and appendeddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 is a side perspective view of a vehicle employing a pre-impactcrash sensing system illustrating an array of infrared (IR) transmitzones, according to one embodiment;

FIG. 2 is a side perspective view of the vehicle employing thepre-impact crash sensing system showing an array of receiverphotodetection zones, according to one embodiment;

FIG. 3 is a top view of the vehicle further illustrating the IR transmitzones employed in the crash sensing system of FIG. 1;

FIG. 4 is a top view of the vehicle further illustrating the IRphotoreceiver zones employed in the crash sensing system shown in FIG.2;

FIG. 5 is an enlarged view of an integrated IR transmitter/receiveremployed in the crash sensing system, according to one embodiment;

FIG. 6 is a block diagram illustrating the pre-impact crash sensingsystem, according to one embodiment;

FIG. 7 is a flow diagram illustrating a routine for sensing a pre-impactcollision of an object with the vehicle, according to one embodiment;

FIG. 8 is a rear view of the vehicle showing the IR transmit zonesincluding an additional elevated horizontal IR transmit zone, accordingto one embodiment;

FIGS. 9A and 9B is a flow diagram illustrating a routine for sensing avehicle feature to update a range estimate and a side impact crash,according to one embodiment;

FIG. 10 is a calibration chart illustrating reflected ripple signals asa function of distance for various identified objects, according to oneexample;

FIG. 11 illustrates a U-shaped IR transmit beam superimposed onto thefront of an oncoming vehicle for use in detecting a vehicle fasciafeature(s), according to one embodiment;

FIG. 12 illustrates an array of the U-shaped IR transmit beams shown inFIG. 11 superimposed onto an oncoming vehicle for detecting the vehiclefascia feature(s);

FIG. 13 illustrates receiver output signals and ripple signal infrequency (Hz) as a function of time as the host vehicle drives byanother vehicle, according to one example;

FIG. 14 illustrates the host vehicle traveling relative to a stationarybarrier, lateral displaced vehicles and a lateral approaching vehicle,to illustrate terrain normalization, according to one embodiment;

FIGS. 15A-15E illustrate the passing of a stationary object and terrainnormalization to detect the object as stationary;

FIGS. 15A-A-15E-E are timing diagrams that illustrate normalization of adetected object as it passes through detection zones A1-A3 shown inFIGS. 15A-15E, respectively;

FIGS. 16A-16D illustrate the passing of an angled stationary object andthe terrain normalization for detecting the stationary target;

FIGS. 16A-A-16D-D are timing diagrams illustrating terrain normalizationas the angled object passes through the detection zones shown in FIGS.16A-16D, respectively;

FIGS. 17A-17D illustrate terrain normalization on an object movinglaterally with respect to the host vehicle, according to one example;and

FIGS. 18A-18C illustrate a routine for providing terrain normalization,according to one embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1-5, a vehicle pre-impact crash sensing system 20 isgenerally illustrated employed on a host vehicle 10, according to oneembodiment. The crash sensing system 20 is shown and described hereinconfigured to detect a pre-impact collision of an object (e.g., anothervehicle) with the vehicle 10, particularly on one or both lateral sidesof the vehicle 10. However, it should be appreciated that the crashsensing system 20 may be employed to detect a pre-impact event on anyside of the vehicle 10, including one or both lateral sides, the frontside and the rear side.

The host vehicle 10 is generally shown as an automotive wheeled vehiclehaving opposite lateral sides and exterior side view mirror housings 12on opposite lateral sides. In the embodiment shown and described herein,the crash sensing system 20 generally includes an integrated infrared(IR) transmitter/receiver 25 shown mounted generally in one of themirror housings 12 of the vehicle 10, at a position sufficient to detectobjects located adjacent to the corresponding lateral side of thevehicle 10. While lateral crash sensing is shown and described hereinfor sensing a collision on one side of the host vehicle 10, it should beappreciated that the crash sensing may also be employed on the oppositelateral side of the vehicle. Further, while the transmitter/receiver 25is shown mounted in the mirror housing 12, it should be appreciated thatthe integrated transmitter/receiver array 25 may be located at otherlocations on the vehicle 10 and positioned to detect one or more objectsin the desired vicinity of the vehicle 10.

The IR transmitter/receiver 25 includes a plurality of IR transmitters(22A-22I) and a plurality of IR receivers 24A-24I, as shown in FIG. 5.As seen in FIGS. 1 and 3, the IR transmitters 22A-22I transmit infrared(IR) energy signals within designated transmit beam patterns 32A-32I ina three-by-three (3×3) array spaced from the lateral side of the hostvehicle 10, according to one embodiment. The infrared transmitter array25 has a plurality (e.g., nine) of infrared transmitters 22A-22I fortransmitting infrared radiation signals within designated correspondingtransmit zones 32A-32I. The transmitter array is activated tosequentially transmit infrared radiation signals in one zone at a time,such as zone 32A, and then switches sequentially to the next zone, suchas zone 32B, and then to zone 32C, and continues through the entirearray to zone 32I, and cyclically repeats the process at a high rate ofspeed, e.g., less than three milliseconds per zone. Alternately,multiple transmit zones could be illuminated simultaneously. In theembodiment shown, the IR transmit zones 32A-32I are oriented in athree-by-three (3×3) array having three rows and three columns, eachzone having a generally conical shape extending from thetransmitter/receiver 25 shown located in the mirror housing 12 andoriented toward the roadway to the lateral side of the host vehicle 10such that the row of zones 32A-32C is spaced further away from the hostvehicle 10 as compared to the row of zones 32D-32F and row of zones32G-32I. Each IR transmit zone 32A-32I has a generally cone shape beamwith a circular cross section which appears more as an elliptical shapeas it impinges at an angle on the ground on the adjacent roadside. EachIR transmit zone 32A-32I has a size sufficient to cover the intendeddetection zone at the lateral side of the host vehicle 10 and may bespaced from the adjacent zones by a predetermined angle, according toone embodiment. According to another embodiment, the IR transmit zones32A-32I may overlap each other, thereby offering intermediary zones thatcan be further processed.

The crash sensing system 20 also includes a receiver array having aplurality of photosensitive receiver elements 24A-24I as shown in FIG.5. In one embodiment, the receiver elements 24A-24I receive and detectslight intensity including reflected infrared radiation signals withincorresponding IR receive zones 34A-34I as shown in FIGS. 2 and 4. The IRreceivers 24A-24I essentially receive light including infrared radiationsignals reflected from one or more objects within the corresponding IRreceive zones 34A-34I and converts the detected light intensity to afrequency output. In one embodiment, the receive zones 34A-34I arearranged in a three-by-three (3×3) array having three columns and threerows that are located such as to substantially align with thecorresponding three-by-three (3×3) array of IR transmit zones 32A-32I.

In addition, the vehicle 10 is shown in FIG. 1 having an additional ortenth IR transmitter 26 shown illuminating a horizontal beam at anelevation where an oncoming vehicle bumper or grille would be expectedto be located. The additional IR transmitter 26 transmits asubstantially horizontal IR calibration beam outward from the lateralside direction of the host vehicle 10 as shown in FIG. 8. In theembodiment shown, IR transmitter 26 is located in a passenger door ofthe host vehicle 10 at a height similar to or the same as the elevationof the beam 28 relative to the ground. It should be appreciated that thetransmitter 26 may be located elsewhere on host vehicle 10 such as inthe front quarter panel or the front or rear bumpers of host vehicle 10.The additional IR transmit beam 28 provides a horizontal calibration IRbeam which is illuminated by itself in the timing sequence ofilluminating the nine IR transmitters 22A-22I. By illuminating theadditional IR transmitter 26, the IR receivers 24A-24I may detect lightintensity including infrared radiation reflected from objects in thecorresponding zones 34A-34I, particularly for object features located atthe elevation of beam 28 such as a vehicle bumper, a vehicle grille orfascia or other features expected to be detected at that elevation. Byproviding the extra horizontal IR transmit beam 28, triangulation of thecalibration beam with the other nine scanned IR beams 32A-32I allowsranging and a measure of the reflection coefficient of the surface of atarget object. As such, enhanced range information may be acquired,according to one embodiment.

Further, the host vehicle 10 is shown in FIG. 2 having an optionaladditional IR photoreceiver 27 shown located at the same or in closeproximity to IR transmitter 26 for receiving reflected signals within ahorizontal beam at an elevation where an oncoming vehicle bumper orgrille would be expected to be located. The IR receiver 27 receive lightsignals including reflected IR signals within receive beam 29 andgenerates a frequency output as a function of the detected lightamplitude. It should be appreciated that with the additional IRtransmitter 26 turned on, either the additional IR photoreceiver 27 orthe individual IR photoreceivers 24A-24I may be employed to detect thepresence of an object within the horizontal beams at the elevation wherean oncoming vehicle bumper or grille is expected which enables enhancedrange estimation based on triangulation of the received signals.

In operation, the array of IR transmitters 22A-22I transmits infraredradiation signals within the corresponding IR transmit zones 32A-32I,one zone at a time, according to one embodiment, resulting in thetransmission of sequential IR signals to the transmit zones, while thereceiver array 24A-24I receives light energy including reflectedinfrared radiation signals from objects located within the correspondingIR receive zones 34A-34I. The detected light signals are output asfrequency signals which are then processed by a processor. By knowingwhich one of the IR transmit zones 32A-32I is illuminated with infraredradiation at a given point in time, the location and range of thedetected object can be determined. As an object moves, the progressionof the object through multiple zones can be monitored to determine speedand direction of the object, such that a processor may determine whethera pre-impact event of the object with the host vehicle 10 is detected.In addition to the sequential illumination of IR transmitters 22A-22I,the system 20 may also activate the additional IR transmitter 26 as partof the sequence to detect objects within the illuminated horizontal IRcalibration beam 28. The sequence of illumination may include successiveactivation of the nine IR transmitters 22A-22I, the activation of thetenth IR transmitter 26, then all IR transmitters turned off, and thenrepeat the cycle.

With particular reference to FIG. 5, the integrated IRtransmitter/receiver 25 is illustrated, according to one embodiment. TheIR transmitter/receiver 25 is shown generally having a housing 60containing an array of nine IR LEDs 22A-22I mounted onto the top side ofa circuit board 62. The IR LEDs 22A-22I may be disposed behindrespective beam-forming optics, which may include reflecting (e.g.,parabolic reflector) and/or refracting optical elements or an aperturefor defining the conical-shaped beam pattern. It should be appreciatedthat the IR transmitter array 22A-22I may employ any of a number ofsignal transmitting elements for illuminating multiple transmit zones,and may be configured in any of a number of shaped and sized beampatterns. According to one example, the IR LEDs 22A-22I may employs acentral wavelength of about 850 nanometers. One example of acommercially available IR LED is available from OSRAM OptoSemiconductors Inc., sold under the brand name Golden Dragon.

The IR transmitter/receiver 25 is shown employing nine photodetectors24A-24I which serve as photosensitive receivers and are shown mounted onthe bottom side of the circuit board 62. Photodetectors 24A-24I maygenerally be placed behind corresponding receiving lenses and/orreceiving reflectors (e.g., parabolic reflectors). The receiving lensesmay include reflecting and/or refracting optical elements that focus thereflected infrared radiation received from the corresponding IR receivezones 34A-34I onto the photodetectors 24A-24I, respectively. Thereceiver array may employ any number of a plurality of receiver elementsfor receiving reflected IR signals from objects within the correspondingnumber of receive zones 24A-24I and may each be configured in a coneshape or other shapes and sizes. One example of a photodetector is alight-to-frequency converter commercially available from Texas AdvancedOptoelectronic Solutions (TAOS). The light-to-frequency converterprovides a frequency output (Hz) as a function of the amplitude of thedetected light radiation.

Referring to FIG. 6, the crash sensing system 20 is further illustratedemploying a microprocessor 50 having various inputs and outputs. Themicroprocessor 50 is shown providing outputs to the nine IR transmitters22A-22I and the tenth IR transmitter 26. The microprocessor 50 outputsLED strobe signals to the IR LEDs 22A-22I and 26 to activate the IR LEDsin a cyclical pattern. Signals indicating light and reflected infraredradiation received by each of the receiver elements 24A-24I are input tothe microprocessor 50. In the embodiment disclosed, the receiverelements 24A-24I provide frequency signals input to the microprocessor50 in the form of a beam IR signature. The beam IR signature includesfrequency (in hertz) representing the amplitude of the photo or lightenergy detected by its irradiance on the receiver from within a givendetection zone.

In addition, the microprocessor 50 receives an input from a passivethermal far IR receiver 46. The passive thermal far IR receiver 46detects emitted radiation within a relatively large area and serves as asafing input that may be logically ANDed with a processor generatedoutput signal to provide risk mitigation for high target certainty.Alternately, the crash sensing system 20 may employ radar or anultrasonic transducer as the safing input. Further safing inputs mayinclude a steering wheel angular rate, yaw, external lateral slip,lateral acceleration and lateral velocity signals, amongst otherpossible safing inputs.

The crash sensing system 20 further includes memory 52, includingvolatile and/or non-volatile memory, which may be in the form of randomaccess memory (RAM), electrically erasable programmable read-only memory(EEPROM) or other memory storage medium. Stored within the memory 52 isa sensing routine 100 for processing the sensed data and determining apre-impact event as described herein. Also stored in memory 52 andexecuted by microprocessor 50 is a routine 200 detecting vehiclefeatures and determining a pre-impact event and a routine 300 performingterrain normalization and determining a pre-impact event.

Additionally, the microprocessor 50 provides a resettable countermeasuredeploy output signal 54 and a non-resettable countermeasure deployoutput signal 56. The countermeasure deploy output signals 54 and 56 maybe employed to mitigate the effects of an anticipated collision.Examples of countermeasure deploy activity may include deploying apretensioner for one or more seat belts, deploying one or more air bagsand/or side air bag curtains, controlling an active suspension or othervehicle dynamics adjustment, or further may activate othercountermeasures on board the host vehicle 10. These are otherdeployments may be initiated early on, even prior to an actual impact.Further, the microprocessor 50 receives vehicle speed 58 which may be ameasured vehicle speed on a vehicle speed estimate. Vehicle speed 58 maybe employed to determine whether or not a lateral impact with an objectis expected and is further employed for terrain normalization todetermine whether or not an object is stationary despite its shape andorientation.

The sensing routine 100 is illustrated in FIG. 7 for sensing ananticipated near impact event of an object with the host vehicle.Routine 100 begins at step 102 to sequentially transmit IR beams, andthe proceeds to step 104 to monitor received photosensitive beams withinthe array of coverage zones. This occurs by sequentially applying IRradiation within each of the transmit beams and receiving light energyincluding reflected IR signals from the receive zones. Next, routine 100performs noise rejection on the beam data that is received. In decisionstep 108, routine 100 determines if the temporal gating has been metand, if not, returns to step 102. The temporal gating bracketingrequirements may take into consideration the path, trajectory and rateof the object, the number of pixels of area, the inferredmass/volume/area, the illumination consistency, and angular beam spacingconsistency.

According to one embodiment, temporal gating requirements are determinedbased on comparison of an object's perceived motion (detection from onecontiguous coverage zone to another) across the coverage zones to theexpected relative speed of potential collision objects of interest(e.g., an automotive vehicle moving at a closing speed of 10 to 65kilometers per hour (kph) or 6 to 40 miles per hour (mph) to a hostvehicle's lateral side). The “range rate” of distance traveled per unittime of a potential collision object can be determined by the detectionassessment of contiguous coverage zones for range rates consistent withan expected subject vehicle's closing speed (i.e., if an object isdetected passing through the coverage zones at a rate of 1 observationzone per 70 milliseconds and each coverage zone is 0.3 meters indiameter perpendicular to the host vehicle's lateral side, then theclosing speed or range rate is approximately 4 meters per second, and isequivalent to approximately 15 kph or 10 mph). Objects moving at rangerates slower or faster than the expected range rate boundary through thecoverage zones would not pass the temporal gating requirement.

Additional assessment can be made based on the quality of the receivedsignal of a potential object as it passes through the coverage zones. Ifthe amplitude of the detected signal varies substantially from onecontiguous coverage zone to another (even if all signals are above athreshold value), it could indicate an off-axis collision trajectory orperhaps an object with a mass not consistent with a vehicle. The signalfidelity and consistency through the contiguous coverage zones can beused to verify a potential vehicle collision.

If the temporal gating has been met, routine 100 then proceeds todecision step 110 to determine if the far IR safing has been enabledand, if not, returns to step 102. If the safing has been enabled,routine 100 proceeds to deploy an output signal indicative of a sensedpre-impact event in step 112. The output signal may be employed toactivate deployment of one or more countermeasures.

The crash sensing system 20 creates a three-dimensional space extendingfrom the lateral side of the host vehicle 10 by way of an array of highspeed sequentially illuminated and scanned infrared light signalsprovided in dedicated coverage zones directed to the lateral side of thehost vehicle 10. Objects which appear within the coverage zones arescanned, and their location, range, speed, and direction are determined.In addition, the size of the object may be calculated. Further, theshape of the object and one or more features such as reflectivitypresent on the object may further be further determined. It should beappreciated that feature identification, such as may be achieved bymonitoring reflectivity, such as that due to color, and othervariations, may be detected and an enhanced range may be determined. Theprocessor 50 processes the information including location, range, speedand direction of the object in addition to the host vehicle speed, anddetermines whether or not a detected object is expected to impact theside of the host vehicle 10. The processor 50 processes the location ofthe detected object, range to the detected object, speed of the detectedobject, and direction of the detected object in relation to the hostvehicle 10 and the speed of the host vehicle 10. Additionally, theprocessor 50 may further process the size and shape of the object inorder to determine whether the object will likely collide with the hostvehicle 10 and, whether the object is of a sufficient size to be aconcern upon impact with the host vehicle 10. If the object isdetermined to be sufficiently small in size or moving at a sufficientlyslow rate, the object may be disregarded as a potential crash threat,whereas a large object moving at a sufficiently high rate of speedtoward the host vehicle 10 may be considered a crash threat.

While the crash sensing system 20 is described herein in connection withan integrated IR transmitter/receiver having nine IR transmitters andnine photosensitive receivers each arranged in an array ofthree-by-three (3×3), and the addition of an additional IR transmitter26 and an optional photosensitive receiver 27, it should be appreciatedthat other infrared transmit and receive configurations may be employedwithout departing from the spirit of the present invention. It shouldfurther be appreciated that other shapes and sizes of coverage zones fortransmitting IR radiation and receiving photosensitive energy radiationmay be employed and that the transmitters and/or receivers may belocated at various locations on board the host vehicle 10. U.S. PatentApplication Publication No. 2009/0099736, entitled “VEHICLE PRE-IMPACTSENSING SYSTEM AND METHOD” discloses various configurations of IRtransmitter and receiver arrays for detecting objects to a lateral sideof a vehicle 10. The aforementioned U.S. Patent Application Publicationis hereby incorporated herein by reference. It should be further beappreciated that variations in segmented lens or reflector designs maybe utilized to provide design flexibility for customized coverage zones.One example of a segmented lens is disclosed in U.S. Patent ApplicationPublication No. 2008/0245952, filed on Apr. 3, 2007 and entitled“SYNCHRONOUS IMAGING USING SEGMENTED ILLUMINATION,” the entiredisclosure of which is hereby incorporated herein by reference.

It should be appreciated that a complete field image encompassing allthe coverage zones may be generated every scan of the entire array ofthe covered volume. By comparing successively acquired photosensedimages, the size, shape, location, range and trajectory of an incomingobject can be determined. To aid in the estimation of the range(distance) of the object from the system 20, and hence the host vehicle10, the additional IR illuminator 26 and optional receiver 27 may beemployed along with triangulation. By employing triangulation, thepresence of an object in the designated zones is compared to theadditional IR transmit zone 28 such that the range (distance) can bedetermined. Additionally, the reflection power of the signal receivedcan be used to enhance the range estimate and thereby enhance thedetection of a pre-crash event.

The vehicle pre-crash impact sensing system 20 employs a featuredetection scheme that identifies certain features of an object vehicle,particularly an object vehicle moving laterally toward the host vehicle10, to provide enhanced vehicle discrimination. According to a firstembodiment of the feature identification scheme, the sensing system 20employs the horizontally illuminated IR calibration beam 28 inconjunction with the IR transmit beams 32A-32I in an attempt to identifya known feature such as bumper and/or grille of a laterally oncomingvehicle. In doing so, the horizontal calibration IR beam transmitter 26is multiplexed between the main IR beams 32A-32I to allow enhanced rangecalibration. By multiplexing the additional IR illumination calibrationbeam 28 with the standard nine IR transmit zones 32A-32I, the range ofthe reflected object can be better estimated. Additionally, by employinga calibration chart, the reflection coefficient of the surface of theobject detected may be used for increased accuracy range estimate, andthus improved risk assessment for proper side air bag deployment orother countermeasure. The optional tenth photosensitive receiver 27 maybe employed to provide received photosensitive signals within zone 29 tofurther enhance the process.

According to another embodiment, enhanced oncoming laterally movingvehicle discrimination can be achieved by employing one or more scannedbeams in a generally U-shape configuration which is generally configuredto encompass the shape of a common vehicle front, particularly thefascia. Multiple U-shaped patterns extending from a distant focus tolarger and nearby may be created with the physical structure of the beamhardware (e.g., via the optical design). Alternately, the beam patterncan be created in software if the number of beams fully covers theoncoming laterally moving vehicle's trajectory path from far to nearby.The U-shaped beam forms may have ends of about three feet by three feetwhich focuses on the oncoming laterally moving vehicle'sheadlamps/signal markers and a center connecting line of about a twofoot height which receives the oncoming laterally moving vehicle'sgrille chrome. Accordingly, the pre-impact sensing system appliesvehicle fascia detection with vehicle front grille shaped opticalregions for improved detection of approaching vehicles. Nine overlappingregions may allow target tracking and relative ranging, and the geometrycan apply to either the IR illumination or light receiver shape orpossibly both the transmit and receiver shapes.

According to a further embodiment, enhanced oncoming laterally movingvehicle discrimination may be achieved by detecting the differentialspectral return of highly reflective vehicle surfaces, such as signalmarkers, headlamps, fog lamps, license plates, chrome and other featurestypical of vehicle front ends. Additionally, background lightillumination levels may also be used to measure the highly reflectivevehicle elements. Additionally, the system 20 may be used to detect theheadlamp on status of the oncoming vehicle further, thereby allowingdiscrimination of their presence as well as any possible pulse widthmodulation (PWM). LED headlamps which are also pulsed may be sensed andused as an additional discrimination element. The geometry of thespectral objects on an inbound oncoming laterally moving vehicle mayalso aid in the discrimination risk assessment.

Referring now to FIG. 9, a routine 200 is illustrated for sensing apre-crash event of a vehicle to deploy one or more devices and includessteps of implementing the various aforementioned embodiments of thevehicle feature identification to advantageously provide updated objectrange estimates. Routine 200 begins at step 202 and proceeds to step 204to illuminate the IR beam N, wherein N is the number of IR transmitbeams which are sequentially activated. Next, in step 206, routine 200stores the IR transmitter that is turned on, and receives the IRamplitude data for the N^(th) receive zone. It should be appreciatedthat the transmit beams are turned on one beam at a time, according toone embodiment, and that the light energy including IR energy reflectedfrom objects within each zone is detected by receivers covering thecorresponding receive zones. In step 208, beam N is turned off as partof this process, and at step 210, the IR off is stored and the amplitudedata of received light energy for beam N is stored with the IR off.Next, N is incremented to the next successive zone of coverage. Atdecision step 214, routine 200 determines if N has reached a value often which is indicative of the number of IR transmitters and, if not,repeats at step 202. Once a complete cycle of all ten zones has beencompleted with N equal to ten (10), routine 200 proceeds to step 216 toindicate that a frame is complete, such that the received energy data ismapped out for the coverage zones.

Once a frame is complete, routine 200 proceeds to step 218 to perform asequential IR modulation signal calculation for each of the IR sensors,shown as sensors 1-9 indicative of the outputs of the respectivephotodetectors 24A-24I. Step 218 essentially performs a sequential IRmodulation signal calculation by taking the difference of the sensedphoto signal while the infrared transmitter is turned on and then whenthe infrared transmitter is turned off for each coverage zone. As such,for zone 1, a signal (X1) is determined based on the difference of thereceive signal with the IR on and the IR off, signal (X2) is indicativeof the receive signal with the IR on minus the IR off, etc. By turningthe IR transmitter array on and off at a frequency such as three hundred(300) hertz, the emitted IR beams are essentially modulated at theswitching or modulation frequency. The difference between the receivedIR energy signals when the IR transmitter is turned on and when the sameIR transmitter is turned off produces a ripple signal as describedherein. The sequential IR modulation signal calculation is performed foreach of the nine zones 1-9 to generate corresponding ripple signals toremove or get rid of the overall background noise.

For an embodiment that employs the tenth IR receiver 27, routine 200performs step 220 which processes the output of the tenth IR receiver 27to acquire enhanced signal to noise ratio. Step 220 is an optional stepthat performs a reference IR modulation signal calculation for the tenthreceiving sensor, also referred to as receiver 27. In doing so, signal(X10) is generated as a function of the IR on minus the IR off for thetenth coverage zone.

Routine 200 then proceeds to step 222 to perform a differential signalcalculation (Y) for each of sensors 1-9 to acquire an enhanceddifferential signal by eliminating or removing background noise. Thedifferential signal calculation involves calculating the differencebetween signal X1 and signal X10, to the extent a tenth transmitter isemployed. Similarly, the signal Y2 is acquired by taking the differencebetween signal X2 and signal X10. Similarly, each of zones 3-9 involvessubtracting the signal X10 from the corresponding received signal forthat zone to provide respective ripple signals for each zone.

Following step 222, routine 200 proceeds to step 224 to use an objectcalibration for vehicle feature identification. According to oneembodiment, routine 200 uses a standard object calibration for a bumperdetection to detect the bumper or similar feature(s) on a lateraloncoming vehicle. According to another embodiment, routine 200 employs ahighly reflective object calibration for fascia and headlamp detection.It should be appreciated that the object calibration for bumperdetection and reflective object calibration for fascia/headlampdetection may be achieved by use of one or more calibration charts orlook-up tables, such as the exemplary calibration chart shown in FIG.10.

The calibration chart shown in FIG. 10 essentially maps a plurality ofdifferent sample objects having various features such as shapes, colors,materials (textures) and reflectivity as a function of the ripple signalin hertz versus range in feet. It should be appreciated that the IRreceiver photodetectors each provide an output frequency dependent uponthe photosensitive detection. The frequency is generally equal to theamplitude (A) of the ripple signal divided by the distance (d) squared(frequency=A/d²). The ripple signals shown are the reduced noise Ysignals generated at step 222. The various targets that are shown bylines or curves 70A-70H in the example calibration table of FIG. 10include arbitrary selected materials such as a white paper, black cottontwill, brick, tree and fog, black paper, black board, black cottongauze, asphalt, and a typical sky scenario. It should be appreciatedthat these and other targets or selected materials may be mapped out ina given calibration table for use with routine 200.

Next, in step 226, routine 200 compares the differential signalcalculations Y to determine the highest correlation for a detectedgeometry. In doing so, routine 200 uses a selected calibration map todetermine the optimum range estimate based on a common range from thenine received ripple signals.

In step 228, routine 200 updates the object range estimate based uponthe identified feature(s). Accordingly, it should be appreciated that byidentifying an anticipated feature for the front end of a lateralapproaching vehicle, such as the vehicle bumper, fascia and/or headlamp,enhanced object range may be estimated for use in the pre-crash sensingsystem 20.

Following the step of updating the object range estimate, routine 200proceeds to decision step 230 to determine if the temporal gating hasbeen met, and if not, returns to step 202. The temporal gating step 230may be the same or similar temporal gating step described in connectionwith step 108 of routine 100. If the temporal gating has been met,routine 200 proceeds to decision step 232 to see if the thermal IRsafing has been enabled and, if so, deploys one or more devices in step234. If the thermal IR safing is not enabled, routine 200 returns tostep 202. The thermal safing step 232 may be the same or similar to thesafing logic described in connection with step 110 of routine 100.

Accordingly, routine 200 advantageously provides for an enhanced objectrange estimate based on the detected type of feature of a vehicle thatis oncoming in the lateral direction. By detecting one or more featuresof the detected object, routine 200 advantageously looks up thecalibration data and provides an updated range estimate whichadvantageously enhances the determination of whether a laterallyapproaching vehicle, such as an automobile, is expected to collide withthe host vehicle 10.

Referring to FIG. 11, the U-shaped geometry for a single beam geometrytransmit beam 32 is shown superimposed onto the front side fasciaportion of the front side of a vehicle, which represents a potentialoncoming laterally moving vehicle. The U-shaped transmit beam 32 may bebroadcast as an infrared beam by a single IR transmitter, according toone embodiment.

According to one embodiment, multiple U-shaped IR transmit beams 32A-32Iare transmit as shown in FIG. 12, each having a generally U-shape andcovering separate zones, which overlap each other. The multiple U-shapebeams may extend from a distant focus to larger and nearby and could becreated with the physical structure of the beam hardware (e.g., via theoptical design).

Alternately, such a beam pattern could be created in software if thenumber of beams fully covers the oncoming laterally moving vehicle'strajectory path from a far distance to a nearby distance. According toone example, the U-shaped beam form may have ends of about three feet bythree feet at distance of about six feet, which focuses on the oncominglaterally moving vehicle's headlamp/signal markers and a centerconnecting line of about a two foot height which receives the oncominglaterally moving vehicle's grille chrome. While an array of U-shapetransmit beams is shown and described herein, it should be appreciatedthat the geometry of the light receivers may be shaped in a U-shapeinstead or in addition to the transmit beams.

By processing the U-shaped beam and the IR signals received therefrom,the trajectory and range of the oncoming vehicle object may be betterdetermined. In an alternate embodiment, the U-shaped beams may be shapedin an oval shape for simplicity, or another shape that picks up thefascia and similar features of the front end of the oncoming vehicle. Itshould be appreciated that as the IR transmit beams cross horizontallythe front fascia of an oncoming front end of a vehicle, a resultantripple signal is generated. The ripple signal is the difference indetected energy signal when the IR is turned on and when the IR isturned off. It should be appreciated that for a high reflectancefeature, such as the headlamps and signal markers, a higher ripplesignal is achieved having a higher frequency. Typically, the centergrille area of a front end of an oncoming vehicle is mainly paint whichhas a lower reflective coefficient versus the reflected components ofthe headlamps and the signal markers. The ripple signal signature can beprocessed to determine the presence of a likely vehicle fascia orportion thereof including the headlamps and signal markers of the frontend of an oncoming vehicle.

The pre-crash sensing system 10 further employs a modulation techniqueto nullify background ambient light conditions and better enhance theestimated target range. The extreme lighting variation from darkness tofull sunlight presents many challenges to an object detection system.These and other deficiencies can be overcome by turning the IR transmitarray on and off at a high frequency of three hundred (300) hertz, forexample, or otherwise provide amplitude modulation of the IR lightsource with a square wave or a sine wave so as to nullify the backgroundambient light conditions and better enhance the estimate of targetrange.

Extreme lighting variations and other deficiencies may be overcome by amodulation technique which measures a scene with ambient lighting andalso with an artificial IR illumination source. The difference betweenthe two measurements provides an inferred target range within the scene.This modulation method provides a very cost-effective method of targetranging, yet does not require extreme power levels as created by typicalsolar exposure which can be cost prohibitive. According to anotherembodiment, the modulation technique may be implemented with a carriersignal as disclosed in U.S. Pat. No. 6,298,311, entitled “INFRAREDOCCUPANT POSITION AND RECOGNITION SYSTEM FOR A MOTOR VEHICLE,” theentire disclosure of which is hereby incorporated herein by reference.

Referring to FIG. 13, the modulation technique is illustrated inconnection with an example of sensed IR and ripple signal both when aparked vehicle is located in the lateral side detection zone of the hostvehicle 10 and when the parked vehicle is removed from the detectionzone. As shown, the sensed raw irradiance or received light energy levelis plotted as a function of time versus frequency as the host vehicledrives by the parked car shown at top at time of about eighteen (18)seconds to a time of about thirty-three (33) seconds, such thatinitially there is no car on the lateral side of the host vehicle upuntil time equals eighteen (18) seconds, and the car passes through thedetection zones and then departs the detection zones at time equalsthirty-three (33) seconds. Initially, sunlight reflected from asphalt isdetected at line 90 and a shadow is detected as indicated. Once theparked vehicle enters the detection zone, the received raw IR irradianceor light energy indicated by area 92 between lines 94 and 96 increasesbetween max and min values when the IR transmitter is turned on at maxborder 94 and when the IR transmitter is turned off at min border 96.The difference between the IR turned on and off signals is representedby the ripple signal 98 which goes from approximately zero (0) frequencyto a frequency of about five thousand (5,000) when the lateral locationvehicle passes through the detection zone, and returns to a value ofnear zero (0) when the lateral located parked vehicle departs thedetection zone. The modulation techniques advantageously allows fordetection of an object due to reflected signal independent of shadow orsunlight.

The data shown in FIG. 13 illustrates frequency data where the objectwas generally in the center of the images and the IR illuminationalternates from on to off. This data yielded a ripple signal 98 ofaround one hundred (100) hertz of variation in the raw data when lookingat the asphalt, and about five thousand (5,000) hertz with a whitetarget at about six (6) feet, according to one example. The ripplesignal 98 did not change even though the ambient lighting moved from afull sun exposure from the time period of about zero to ten (0 to 10)seconds to the shadow of the vehicle at about the time period of aboutseventeen (17) or eighteen (18) seconds. The data shown in FIG. 13 wastaken within a 950 nanometer band which requires rather expensiveoptical bandpass filters to eliminate sunlight. The modulation techniqueallows for operation with a much less costly high wavelength filter,such as greater than 700 nanometers.

Given the ripple signal 98 generated in the table of FIG. 13, themodulation technique enables the range estimation to be enhanced withacquisition from the calibration table shown in FIG. 10. As seen in FIG.10, a white object's range can be fairly well predicted as shown by thecurve 70A representing white paper. Dark objects are also predictable asshown by the curve 70H representing asphalt. Textured fabrics mayexhibit a self-shadowing effect. By use of this inferred rangeinformation and the event progression of the multiple spot data, a sideimpact risk estimate can be made and, if deemed of sufficient risk, theside air bags can be deployed. By monitoring the ripple current 98 shownin FIG. 13, for each coverage zone, the ranges as shown by lines 72A,72B and 72C may be established, for example. By looking at common pointswithin the set of ranges 72A-72C, an enhanced range estimate may beestablished. In the given example, ranges 72A-72C have a common rangevalue of about six feet. Since the frequency output of the IRphotodetectors may vary based upon color or reflectivity in combinationwith a range, an enhanced range estimate may be provided by looking forcommon range values within the zones.

The pre-crash sensing system 10 further employs a terrain normalizationmethod to normalize out stationary objects that pass through thedetection zones to the lateral side of the vehicle 10. Referring to FIG.14, an example driving scenario is shown illustrating a host vehicle 10employing the sensing system 20 is traveling along a roadway relative toseveral objects including an angled barrier 80, a lateral oncomingvehicle 84, a passing lateral vehicle 82, and a laterally projectingvehicle 86 expected to collide with the host vehicle 10. The terrainnormalization method is able to normalize out stationary objects, suchas the angled barrier 80 which, due to its shape, may appear to bemoving toward the host vehicle 10, such that the system 20 may ignorethe stationary object 84 in determining whether or not an impendinglateral collision will occur. By use of range data, which is inherent tothe power level of the reflected signal, a three-dimensional volume canbe estimated with the array of coverage zones 34A-34I. As the hostvehicle 10 is driven forward, the frontmost beams will detect a terrainpass by of an object. This terrain information, including inferreddistance, is propagated to the successive rearward beams which followand is used to normalize out the existence of stationary objects whichare characterized as clutter to be ignored. Objects which have a lateralvelocity component are recognized as potential oncoming targets andtheir characteristics are further evaluated for assessed threat of alateral collision to the host vehicle 10.

In particular, physical objects such as an angled barrier (e.g., aguardrail) or an angled road line may have a shape resembling anoncoming vehicle bumper and can produce similar or identical IR patternsignatures which possibly could cause undesirable deployment of an airbag or other device when not properly detected. The terrainnormalization method attempts to detect and eliminate such falsetriggers. With the transmitter and receiver arrangement shown, a matrixof infrared beams and receiving beams illuminate the side of the hostvehicle 10 to provide a sensed volume by the three-by-three (3×3) array.Using range data, which is inherent to the power level of the reflectedsignal, a three-dimensional volume can be estimated. As the host vehicle10 is driven forward, the frontmost beams or zones will see the terrainpass by first. This terrain information includes distance that ispropagated to subsequent following beams which follow behind inprogression and are used to normalize out stationary objects. Objectswhich have a lateral velocity component are recognized as potentialoncoming targets to the host vehicle 10, and their characteristics arefurther evaluated for assessed threat to the host vehicle 10.

Each scan of the matrix yields an object light level for each spot ofthe zones detected. From this, the range (distance) of an object can beinferred according to a distance look-up table. Generally, objects whichare at ground level are quite low in reflected energy as power isrelated to one divided by the distance squared. As seen in FIG. 14,barriers and oncoming cars illuminated by using the leading spot zonesand propagating this information rearward to the trailing spots isachieved with a normalization technique. The data may be processed byaveraging, normalization, and time differential, amongst otherembodiments. Additionally, road speed and steering angle could be usedto propagate the optical distance of the measured lead objects rearward,thus, eliminating them from causing false deployments. In a similarmanner, the detection of objects entering the rearmost zones first areprocessed in reverse, such as when a car passes the host vehicle 10. Theresultant matrix of processed data which has been normalized to removeoncoming and passing objects is used to evaluate the event propagationof a lateral object, such as an oncoming laterally moving vehicle 86.

Referring to FIGS. 15A-15D, the progression of a stationary object isillustrated as a host vehicle 10 passes by stationary object 84. As seenin FIG. 15A, the stationary object 84 is in front of the nine detectionzones. As the host vehicle 10 moves forward to the lateral side of astationary object 84, the stationary object 84 is shown first beingdetected by zone A1 in FIG. 15B, and then detected by both zones A1 andA2 in FIG. 15C, and then detected by zones A1-A3 in FIG. 15D. Finally,as the object 84 departs at least part of the detection zone, the object84 is shown in FIG. 15E departing zone A1 and is still detected in zonesA2 and A3. In this scenario, the system 20 employs a normalizationroutine to subtract out the propagated signal detected in a forwardlocated zone from the raw data in an attempt to detect whether or not alateral motion of the object is occurring. As seen in FIGS. 15A-A-15E-E,the detection of the object 84 in zone A1 is detected and as itapproaches zone A2, the propagated signal of zone A1 is subtracted fromthe raw data of zone A2 to provide a normalized result indicative of astationary object which should be rejected.

Referring to FIGS. 16A-16D, a scenario is shown in which a stationaryobject 80 in the form of an angled barrier, for example, is passed bythe host vehicle 10 and the system 20 employs terrain normalization toreject the stationary object 80, despite its potentially deceiving shapedue to its angle towards the vehicle 10. In this example, the stationaryobject 80 first enters zone A1 in FIG. 16A, and then proceeds to enterzone A2 in FIG. 16B. In FIG. 16C, the stationary object 80 is detectedby zones A1, A2 and B1, and then in FIG. 16D, the stationary object 80is detected primarily in zones A3, B2 and C1. As the stationary objectpasses from zone A1 through and into zones A2, A3 and B1, the terrainnormalization subtracts the propagated signal of the leading zone fromthe following zone. For example, in zone A2, the normalized result isthat the propagated signal of zone A1 is subtracted from the raw data ofzone A2 to determine that the stationary object 80 is detected andshould be rejected. The propagated signal is subtracted based on a delaytime which is determined based on the speed of host vehicle 10, suchthat the signal data of the preceding zone captures an area of spacethat is also captured in the following zone. The terrain normalizationthereby takes into consideration the detected signal information fromthe preceding zone taking into consideration the time delay and thespeed of the host vehicle 10.

Referring to FIGS. 17A-17D, a further example of a laterally oncomingvehicle 86 is illustrated in which the laterally oncoming vehicle 86first enters zone A1 and A2 in FIG. 17B and proceeds into zones B1, B2,A1, A2 and C1 in FIG. 17C, and finally proceeds into zones A1, A2, B1,B2 and C1-C3 in FIG. 17D. The terrain normalization effectively removesstationary objects so that the system 20 can detect that the laterallyoncoming vehicle 86 is not stationary, but instead is moving with alateral velocity component toward the host vehicle 10, such that anoncoming collision may occur.

Referring to FIGS. 18A-18C, the terrain normalization routine 300 isillustrated, according to one embodiment. The terrain normalizationroutine 300 begins at step 302 and proceeds to step 304 to illuminatethe outermost row of IR transmit beams in zones A1, A2 and A3. Next, instep 306, routine 300 receives the IR amplitude data for receive zonesA1, A2 and A3 while the IR is turned on. Next, the IR transmit beams forzones A1, A2 and A3 are turned off. Proceeding to step 310, routine 300receives the IR amplitude data for zones A1, A2 and A3 while the IRtransmit beams are turned off and stores the received amplitude datawhile the IR transmit beams for zones A1, A2 and A3 are turned off. Atstep 312, routine 300 turns on the IR transmit beams for the next ormiddle row of zones B1, B2 and B3. In step 314, routine 300 receives theIR amplitude data for zones B1, B2 and B3 while the IR transmit beamsare turned on and stores the received IR amplitude data in memory. Atstep 316, routine 300 turns off the IR transmit beams for zones B1, B2and B3. With the IR transmit beams turned off, routine 300 proceeds tostep 318 to receive the IR amplitude data for zones B1, B2 and B3 andstores the received IR amplitude data in memory.

Routine 300 proceeds to step 320 to turn on the IR transmit beams forthe third or closest row of zones C1, C2 and C3. Next, at step 322,routine 300 receives the IR amplitude data for zones C1, C2 and C3 andstores the received IR amplitude data in memory. In step 324, routine300 turns off the IR transmit beams for zones C1, C2 and C3. With the IRtransmit beams turned off, routine 300 proceeds to step 326 to receivethe IR amplitude data for zones C1, C2 and C3 and stores the received IRamplitude data in memory. Next, routine 300 turns on the IR transmitbeam for the tenth or additional transmit beam at step 328. With thetenth or additional IR transmit beam turned on, routine 300 proceeds tostep 330 to receive the IR amplitude data for zones A1, A2, A3, B1, B2,B3, C1, C2, C3, and the tenth receiver while the tenth or additional IRtransmit beam is turned on. Finally, the initial frame is complete atstep 332.

Once the frame is complete, routine 300 proceeds to step 334 to performa sequential IR modulation signal calculation X for each of sensors onethrough nine, shown labeled A1-C3. This includes calculating thedifference in signals when the IR transmit beam is turned on and whenthe IR transmit beam is turned off for each of zones A1-C3 to provide araw ripple signal for each of zones A1-C3.

Proceeding on to step 336, routine 300 stores a history of the IRmodulation signal calculation (X) for each of sensors one through ninefor zones A1-C3. This involves storing the time average of the IRsignals for each of the zones A1-C3.

At step 338, routine 300 looks at the forward vehicle motion and cancelsout the stationary signals from the following sensor locations. Thisincludes normalizing the signal for a given zone by subtracting out fromthe following zone the history of the previous zone. For example, thehistory of zone A1 is subtracted from zone A2 when an object passes fromzone A1 to zone A2. The continued signal normalization applies to zoneA3 in which the history from zones A1 and A2 is subtracted from zone A3at the appropriate time based upon a time delay based on the vehiclespeed. The time delay is based on vehicle speed so that the zones coverthe same area of space. Signal normalization also occurs in rows B and Cby subtracting out the signal from the prior zone. It should beappreciated that the same signal normalization applies in the reversedirection for a vehicle or object passing laterally from the rear of thehost vehicle 10 toward the front of the host vehicle 10, except thesignal normalization is reversed such that the propagating signal inzone A3 is subtracted from A2, etc. For example, for zone A2, you takethe current X2 data and subtract off the history of zone A3 such that asliding window essentially is provided. The terrain normalizationessentially eliminates the fore and aft movement parallel to the hostvehicle 10 in the detection zones. By doing so, stationary objects orclutter are rejected.

Routine 300 then proceeds to step 340 to determine the lateral componentof the moving object. The lateral component of an object is based on thelateral movement toward or away from the lateral side of the hostvehicle 10. Next, in decision step 342, routine 300 determines if thereis lateral velocity component greater than eighteen miles per hour (18mph) and if the object is large enough and, if so, proceeds to step 346to update the object range estimate, and then proceeds to decision step348 to check the temporal gating. If the object is not large enough orif the lateral velocity component is not greater than eighteen miles perhour (18 mph), routine 300 returns to step 302. At the decision step348, temporal gating is compared to determine whether or not an objectis likely to collide with the host vehicle 10 and, if so, routine 300proceeds to decision step 350 to determine if thermal IR safing isenabled and, if so, deploys an output at step 352. If the thermal IRsafing is not enabled, routine 300 returns to step 302. It should beappreciated that the temporal gating of step 348 and the thermal IRsafing of step 350 may be the same or similar to those steps provided inroutine 100 as discussed above.

While a thermal far IR safing receiver 46 is shown and described hereinfor providing thermal IR safing, it should be appreciated that othersafing techniques may be employed to eliminate false triggers. Asdescribed, a matrix of IR beams illuminates the side of host vehicle 10to provide a sensed volume. A single IR beam may be provided in a matrixof beams. Using range data, which is inherent to the power level of thereflected signal, a three-dimensional volume can be estimated. Theaddition of a separate technology to “safe” the primary deploy signal isrequired to ensure against false air bag deployment. “Safing” is definedas a complementary measure to verify that the detected object is anoncoming laterally moving vehicle where the measured speed of theoncoming laterally moving vehicle matches the speed measured by theprimary detection. Moreover, the measured speed may be approximatelyfifteen (15) to fifty (50) miles per hour, according to one example.Additionally, this concept of lateral velocity verification can be usedto enable sub-fifteen mile per hour air bag deployment.

Use of discrimination sensors to assess data to do a lateral velocitycalculation of the oncoming laterally moving vehicle compared to thesafing lateral velocity may be provided. If the two are similar, it canbe assumed with a high degree of confidence that the oncoming object isindeed a sufficient threat to the occupants of the host vehicle 10.Objects which have a significant lateral velocity component, such asthose greater than eighteen (18) miles per hour, may be recognized aspotentially dangerous targets and their characteristics may be evaluatedfor assessed threat to the host vehicle 10. Each scan of the matrixyields an object light level for each spot or zone. An analysis of thelight levels from all the spots can infer the distance, velocity andtrajectory of an object from the host vehicle 10.

Discrimination technology considered for the safing technique caninclude active near IR (NIR) radar, or camera. One or more safingtechnology and one or more deploy technology may be utilized in thedesign.

Individual safing or deploy technologies can include active near IR, farIR (FIR), ultrasonic acoustics, laser time-of-flight sensor (3Dscanner), 3D camera, or stereo camera.

Employing the thermal IR safing technique, heat may be detected from anoncoming vehicle. According to an ultrasonic sensed safing technique,ultrasonic sensors perform the safing function. The safing function isemployed to ensure the event progression is due to an incoming vehicleand not due to other situations that would not require a side air bagdeployment. Safing may prevent deployment of a side air bag when thehost vehicle 10 strikes a stationary object, such as a tree, pole orparked vehicle. These objects are not likely to have the thermalsignature of a moving vehicle, and in extreme yaw conditions, may notreturn a steady ultrasonic return which is especially true for trees andpoles. Therefore, there is a need to relate a means to disable or reducesafing requirements in yaw conditions.

Situationally dependent safing is a method to modify side air bagpre-impact deployment safing based upon the vehicle stability. Duringnormal vehicle conditions, an active IR sensing system is employed todetermine when a side impact is imminent. Supplemental information fromeither an ultrasonic or passive IR system is used for safing. If thehost vehicle 10 path is tangent to its four-aft direction or the targetfollows a linear path into the side of the host vehicle 10, incomingtargets will follow a normal progression and safing techniques willprovide information necessary to make a reliable decision. A relativelylinear progression will allow sufficient path information of the activeIR system to generate a mature path. In extreme yaw conditions, however,the path of the host vehicle 10 may not allow the development of amature track for impacts. Moreover, the supplemental safing sensors areless likely to provide adequate information to supplement the deploymentcondition. If an ultrasonic sensor is employed, the host vehicle 10 mayspin into the target too quickly to provide an adequate return. If apassive IR system is employed, the target may not generate the thermalsignature necessary to allow deployment. Therefore, a decision tree mayallow for safing levels to be reduced in cases where the host vehicle 10is not following a consistent path due to the high yaw. The decisiontree may include logically ORing the following requirements: Far IR(FIR) is greater than threshold, steering wheel angular rate is greaterthan N degrees per second, yaw is greater than N degrees per second,external lateral slip divided by yaw, and lateral acceleration greaterthan 0.5 g. The output of the OR logic is then logically ANDed with thediscrimination output to determine whether or not to deploy one or moredevices.

Additionally, vehicle travel direction can be inferred by the groundterrain monitoring of the active IR scanning system. By use of both leftand right pre-crash side sensors to monitor the optical flow of asphaltpattern directions, the vehicle velocity and direction including lateralsliding can be detected and approach countermeasures initiated. Underinclement conditions, such as blowing snow/rain/sand side slipmonitoring is failed-safed by a lateral yaw rate sensor. Lateral slidinginformation can be used for side air bag threshold lowering, stabilitycontrol, or potentially rollover detection. The lateral slip sensor mayuse a left or right sensor to monitor road pattern directions. With thetransmit/receive beams, an optical flow through beam matrix determinesground travel direction, vehicle rotation and potential vehicle roll.

As mentioned herein, the array of transmit and receive IR beams may bearranged in an overlapping configuration. Tailoring of three-dimensionalvolume to the side of the host vehicle 10 can pose a challenge to ensurean oncoming laterally moving vehicle is detected and a side air bag isdeployed, yet allow the numerous no-deploy objects which pass harmlesslyby the host vehicle 10 to not cause false deploys. The beam overlap mayallow increased spatial resolution with a minimum number of discretebeams by use of the beam overlap. In order to increase the effectivespots or zones of a pre-crash side impact sensor without adding morechannels, each of the nine beam spots may be enlarged to allow a twentypercent (20%) beam spot overlap which provides twenty-one multiplexedzones, in contrast to the above disclosed nine non-overlap zones, whichallows increased distance resolution of the incoming object. Thegeometry can apply to IR illumination or light receiver shape orpossibly both transmitter and receiver shapes for more resolution.Accordingly, the beam overlap method may consist of overlapping scannedareas or regions to allow increased target tracking resolution.

Accordingly, the pre-crash sensing system 20 of the present inventionadvantageously detects an impending collision of an object with the hostvehicle 10, prior to the actual collision. The crash sensing system 20is cost affordable and effective to determine whether an object isapproaching the host vehicle 10 and may collide with the vehicle,sufficient to enable a determination of the impending collision prior toactual impact. Further, the pre-crash sensing system 20 may determinewhether the object is of sufficient size and speed to deploy certaincountermeasures.

It will be understood by those who practice the invention and thoseskilled in the art, that various modifications and improvements may bemade to the invention without departing from the spirit of the disclosedconcept. The scope of protection afforded is to be determined by theclaims and by the breadth of interpretation allowed by law.

1. A vehicle pre-impact sensing system comprising: an array of energysignal transmitters mounted on a vehicle for transmitting energy signalswithin multiple transmit zones spaced from the vehicle; an array ofreceiver elements mounted on the vehicle for receiving the signalsreflected from an object located in one or more multiple receive zonesindicative of the object being in certain one or more receive zones; anda processor for processing the received reflected signals anddetermining range, location, speed and direction of the object, whereinthe processor modulates the transmit energy signals and determines adifference in sensed signals for each zone with the transmitters turnedon and turned off, said processor further determining whether the objectis expected to impact the vehicle as a function of the determined range,location, speed and direction of the object, and generates an outputindicative of a sensed pre-impact event.
 2. The sensing system asdefined in claim 1, wherein the transmit energy signals are modulated byturning the transmitters on and off at a modulation frequency.
 3. Thesensing system as defined in claim 1, wherein the modulation is at arate of about 300 Hz.
 4. The sensing system as defined in claim 1,wherein the difference in sensed signals provides a ripple signal,wherein the ripple signal is compared to a calibration table to detect afeature of the object.
 5. The sensing system as defined in claim 1,wherein the array of energy signal transmitters comprises an array oflight transmitters.
 6. The sensing system as defined in claim 5, whereinthe array of light transmitters comprises an array of infraredtransmitters configured to emit infrared radiation in designatedmultiple transmit zones.
 7. The sensing system as defined in claim 6,wherein the array of receiver elements comprises an array ofphotodetectors for receiving reflected infrared radiation, wherein thephotodetectors receive light signals including reflected signals fromthe designated receive zones.
 8. The sensing system as defined in claim1, wherein the system senses an object on a lateral side of the vehicle.9. The sensing system as defined in claim 1, wherein the processorfurther determines size of the object, and wherein the processorgenerates an output signal indicative of a sensed pre-impact eventfurther based on the determined size of the object.
 10. The sensingsystem as defined in claim 1 further comprising an additional signalreceiver for receiving energy signals within an additional beam, whereinsignals measured with the additional receiver are subtracted from thesignals measured with each of the array of receivers to remove noise.11. The sensing system as defined in claim 1, wherein the transmitterarray and receiver array each comprises a plurality of cone-shapedbeams.
 12. A method of detecting an expected impact of an object with avehicle, said method comprising the steps of: transmitting signals withan array of transmitters within multiple transmit zones incrementallyspaced from the vehicle, within one or more zones at a time; receivingsignals with an array of receivers reflected from an object located inthe one or more multiple receive zones indicative of the object being incertain one or more received zones; processing the received reflectedsignals; determining a location of the object; determining a range tothe object; determining speed of the object; determining direction ofthe object; modulating the transmit energy signals array; determining adifference in sensed signals for each zone with the transmitters turnedon and off; determining whether the object is expected to impact thevehicle as a function of the determined range, location, speed anddirection of the object; and generating an output indicative of thesensed pre-impact event.
 13. The method as defined in claim 12, whereinthe step of modulating the transmit energy signals comprises turningeach of the transmitters on and off at a modulation frequency.
 14. Themethod as defined in claim 13 further comprising the step of determininga ripple signal based on the difference and using the ripple signal todetect a feature of the object.
 15. The method as defined in claim 14,wherein the detected feature of the object is used to enhance thedetermination of range to the object.